This invention relates to the processing of signals transmitted through optical fibers. More particularly the invention is directed to a continuously variable delay line.
The advantages of fiber optic delay lines are well-known in the art. Thus, for example, transversal filters capable of selectively filtering modulated light signals has been taught. Furthermore, the construction of transversal filters by helically wrapping a single fiber optic element around a series of v-grooves in a silicon chip, with taps at each groove, is known in the art. However, because no adjustment of the delay line lengths has been possible in prior art delay lines or transversal filters, the frequency vs. attenuation characteristics of prior transversal filters was of necessity, determined at the time of construction of the filter. There is therefore a need for an adjustable fiber optic delay line so that, for example, the frequency response of a transversal filter utilizing the delay line may be adjusted through a continuous range.